1. Field of the Invention
The present invention relates to a data processing apparatus, an X-ray apparatus, and a data processing method.
2. Description of the Related Art
A medical image diagnostic technique using an X-ray diagnostic apparatus, an MRI apparatus, an X-ray CT apparatus, or the like has rapidly progressed with advances in computer technology of the 1970s. This technique has become indispensable to today's medical care.
X-ray diagnosis has recently improved mainly in the field of cardiovascular with advances in catheter techniques. X-ray diagnosis in a cardiovascular region is aimed at arteries and veins in the whole body. In many cases, X-ray transmission images are captured while a contrast agent is injected in blood vessels. An X-ray diagnostic apparatus for cardiovascular diagnosis generally includes an X-ray generating unit, an X-ray detecting unit, a holding mechanism which holds them, a bed (top), and a signal processing unit. As the holding mechanism, a C-arm or Ω-arm is used. Combining this arm with a top-cantilevered bed makes it possible to perform X-ray imaging from an optimal position or angle for a patient (to be referred to as the subject hereinafter).
As a detector used for the X-ray detecting unit of an X-ray diagnostic apparatus, an X-ray film or an image intensifier has been used. In an X-ray imaging method using this image intensifier, X-ray image information obtained when X-rays generated by the X-ray tube of the X-ray generating unit are applied to the subject and transmitted through the subject is converted into an optical image by the image intensifier. This optical image is captured by an X-ray TV camera and converted into an electrical signal. The X-ray image information converted into the electrical signal is digitized. The resultant image is displayed on a monitor. Therefore, the imaging method using the image intensifier allows real-time imaging which is impossible in the film system, and can acquire image data in the form of digital signals. This makes it possible to perform various kinds of image processing. As a substitute for the above image intensifier, a two-dimensional array X-ray flat panel detector (to be referred to as a flat panel detector hereinafter) has recently attracted attention. Some of such detectors have already been put into practical use.
In a conventional X-ray diagnostic apparatus having a C-arm, an imaging system is operated to set a desired imaging direction by moving the handle provided on a console. For example, in setting a C-arm tilt angle (working-angle) for coronary artery imaging, the following are required: (1) to image a blood vessel to be diagnosed without overlap of another blood vessel thereon; (2) to perpendicularly apply X-rays to the running direction of a blood vessel having a lesion region such as a stenosis region; and (3) to apply X-rays in a direction in which a bent portion can be easily observed. In order to meet such requirements, a doctor or a technician (to be referred to as an operator hereinafter) repeatedly performs X-ray imaging of the subject in a trial and error manner while changing the C-arm tilt angle, and observes the obtained fluoroscopic image data on the monitor, thereby setting an optimal X-ray imaging direction.
As disclosed in, for example, the specification of U.S. Pat. No. 6,424,731 (pages 1 to 4 and FIGS. 1 and 2), there is proposed a method of acquiring the three-dimensional image data of the subject in advance and setting an X-ray imaging direction on the basis of the obtained three-dimensional image data. In this method, the operator sets an optimal imaging direction by observing a three-dimensional image of the subject displayed on the display unit of the apparatus while rotating the image in a predetermined direction. The operator then sets a C-arm tilt angle on the basis of the set optimal imaging direction and performs X-ray imaging. As disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-329729, there is provided a technique in which as a standard organ model is rotated, the arm of an X-ray apparatus rotates in accordance with the rotation of the model, thereby adjusting the angle of the arm. In addition, as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2007-20891, there is provided a technique of indicating the optimal arc of the pivotal movement of an X-ray apparatus in accordance with a point on a model which is designated by clicking.
Assume that when setting an optimal imaging direction for a morbid region such as a blood vessel, an operator who does not have sufficient anatomical knowledge or experience sets a C-arm tilt angle in a trial and error manner. In this case, since X-rays are applied to the subject many times, it takes much time to set a final imaging direction, resulting in an increase in X-ray exposure dose. In addition, since it is necessary to acquire three-dimensional image data of the subject in advance, the problems concerning the time required for overall X-ray imaging and the X-ray exposure dose of the subject have not still solved. Furthermore, in the above technique, it takes much time to determine, for example, an optimal direction so as to obtain images from many directions. In addition, it is difficult to apply this technique to actual patients with individual differences because of the use of a model. The problem of foreshortening cannot be solved because of the use of projected data.
The present invention has been made in consideration of such a situation, and has as its object to provide an X-ray diagnostic apparatus and X-ray imaging method which can shorten the time required for X-ray imaging and reduce the X-ray exposure dose of the subject by setting an optimal imaging direction using image data obtained in advance.